Atomistic Design of Carbon Nanotube Junctions of Arbitrary Junction Geometry

Abstract

Creating any workable materials construct for any viable applications using carbon or any other nanotubes would invariable involve dispersion of the nanotube in either twodimensional spatial mesh or three-dimensional volumetric space. These dispersed nanotubes invariably are interconnected via overlap or junctions. It is known that the atomic configuration of these nanotube junctions critically influence the bulk properties (structural, thermal, electrical, dielectric). Thus, it is extremely important to pay a close attention to how optimally these junctions can be formed to attain the desirable properties. In all practical situations, experimentally synthesized junctions (either single CNT junctions or junctions in 2D and 3D CNT network structures) are expected to have random orientation of defect sites (non-hexagonal rings) around the junction. Such random nature of junctions’ topology and defect characteristics is expected to affect their strength and durability as well as have impact on associated mesoscopic and macroscopic properties. In this work, we present a generic framework on creating junctions between CNTs with arbitrary spatial (orientation and degree of overlap) and intrinsic (chirality) specifications, as well as to tune degree of topological defects around the junction via a variety of defect annihilation approaches. Our method makes use of the primal/dual meshing concept where the development and manipulation of the junction nodes occur using a triangular meshes (primal mesh), which is eventually converted to its dual (honeycomb mesh) to render a fully-covalently bonded CNT junction where each carbon atom has 3 bonded neighbors (mimicking sp¬2 hybridization). This design approach offers an opportunity to investigate the effect of topological arrangement of defects around the junction on mechanical, electrical and thermal properties. In addition, this junction design methodology is applied to a CNT-graphene junction and to study the effect of local carbon defects (pentagonal or heptagonal carbon ring versus the hexagonal) on junction strength. It is observed that a symmetrical distribution of carbon ring defects around the CNT-graphene junction yield higher strength that that of irregular defect distribution.